Aliphatic additives for soot reduction

ABSTRACT

The invention relates to a jet fuel composition for reducing particulate emission in the exhaust from jet engines. The composition includes an aliphatic additive having a boiling point ranging from about 230° C. to about 310° C.

FIELD OF THE INVENTION

The invention relates a jet fuel composition for reducing particulate emissions from jet engines.

BACKGROUND OF THE INVENTION

Jet engines, during the burning of hydrocarbon fuels, produce particulate matter. The production of particulate matter is a concern for a variety of reasons, including human health, the detectability of aircraft, and engine lifetimes.

Particulate matter having a diameter of less than about 10 μm (PM10) is regulated by the National Ambient Air Quality Standards (NAAQS), as particulate matter having a diameter of less than about 2.5 μm has been linked with increased respiratory illness. Particles having a diameter of less than about 0.1 μm are believed to be particularly harmful to humans.

Although not as important for commercial jets, stealth and detection avoidance for military aircraft is of paramount importance. Reducing particulate matter released from the engines of such aircraft would decrease the visible and, potentially the infrared, signature of the aircraft. Additionally, the decreased production of particulate matter may also result in a reduction in engine deposits as the deposition of engine deposits typically depends upon both the particle size and composition, and more efficient combustion would produce less particulate matter, leading to decreased deposits thereof.

Prior methods employed to reduce the production of particulate matter in jet engines have included the removal of impurities from jet fuel, the addition of chemicals to modify the atomization and/or vaporization of the fuel, or chemically changing the combustion process. Some prior art have focused on the use of various additives, such as metal salts of organic compounds, phosphonic and thiophosphonic acids and derivatives thereof, surfactants, oxygenated organic compounds, aromatics, peroxides, and manganese carbonyl compounds in combination with metal containing detergents. Many of the prior art methods, however, suffer in that they are labor intensive, expensive, are inefficient, and/or, in the case of certain additives, reduce the overall energy content of the fuel below acceptable levels. In general, any sort of oxygenate, by nature, will reduce the energy density of the fuel since its partially an oxidizer rather than a fuel. In general principle this will reduce the energy density of the fuel. Thus, for at least the reasons noted above, there exists a need for increased efficiency in jet engines, particularly for a reduction in the production of particulate matter.

SUMMARY

Provided are methods and compositions for reducing particulate matter or soot in jet engine exhaust, when a jet fuel is combusted in a jet engine.

In one aspect, the present invention is directed to a jet fuel composition for producing an exhaust having reduced particulate matter. The composition includes: a jet fuel; and an additive that includes an aliphatic hydrocarbon compound having at least 10 carbon atoms. The aliphatic hydrocarbon additive has a boiling point of between about 230 and 310° C.

In certain embodiments, the jet fuel composition includes jet fuel in an amount of at least 65% by weight and the additive in an amount between about 5 and 35% by weight. In an alternate embodiment, the jet fuel composition includes jet fuel in an amount of between about 80 and 90% by weight and the additive in an amount of between about 10 and 20% by weight. The additive preferably is an aliphatic hydrocarbon having between about 12 and 15 carbon atoms.

In another aspect, the present invention provides a method for reducing particulate matter in an exhaust from a jet engine. The method includes the steps of combusting a jet fuel in a jet engine, wherein said jet fuel includes an additive for reducing the amount of particulate matter present in said exhaust. The additive is an aliphatic hydrocarbon having at least 10 carbon additives and a boiling point of between about 230 and 315° C.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the concentration of particulate matter in jet exhaust as a function of the concentration of an aliphatic hydrocarbon additive in the fuel.

FIG. 2 shows the concentration of particulate matter in jet exhaust as a function of the concentration of an alternate aliphatic hydrocarbon additive in the fuel.

FIG. 3 shows the concentration of particulate matter in jet exhaust as a function of the concentration of a mixture of linear aliphatic hydrocarbon additives in the fuel.

FIG. 4 shows the concentration of particulate matter in jet exhaust as a function of the concentration of an alternate mixture of linear aliphatic hydrocarbon additives in the fuel.

FIG. 5 shows the concentration of particulate matter in jet exhaust as a function of the concentration of a mixture of branched aliphatic hydrocarbon additives in the fuel.

FIG. 6 shows the concentration of particulate matter in jet exhaust as a function of the concentration of an alternate mixture of branched aliphatic hydrocarbon additives in the fuel.

FIG. 7 shows the concentration of particulate matter in jet exhaust as a function of the concentration of an aliphatic hydrocarbon additive having a boiling point of about 175° C.

DETAILED DESCRIPTION OF THE INVENTION

Although the following detailed description contains many specific details for purposes of illustration, it is understood that one of ordinary skill in the art will appreciate that many examples, variations and alterations to the following details are within the scope and spirit of the invention. Accordingly, the exemplary embodiments of the invention described herein are set forth without any loss of generality to, and without imposing limitations thereon, the claimed invention.

In one aspect, the present invention provides an additive composition that includes aliphatic hydrocarbons for reducing particulate matter produced by jet engines. In another aspect, the present invention provides a jet fuel composition that includes an aliphatic hydrocarbon additive for reduced particulate matter production.

As used herein, “aliphatic” refers to non-aromatic hydrocarbon compounds, more specifically, both cyclic and non-cyclic non-aromatic hydrocarbon compounds. Aliphatic compounds can be straight chains, or alternatively can be branched. Aliphatic compounds, as used herein, can include at least one double or triple bond. Exemplary non-aliphatic compounds include dodecane, tridecane, tetradecane, pentadecane, hexadecane and heptadecane. Exemplary aliphatic cyclic compounds for use herein include cyclodecane, substituted cyclodecanes, bicyclohexyl and decahydronaphthalene.

Jet fuels, as used herein, are aviation fuels designed for use in aircraft with gas-turbine engines. Exemplary civilian jet fuels include Jet A, Jet A-1, and Jet B, each of which includes a mixture of different hydrocarbons, including both aliphatic and aromatic hydrocarbons. Exemplary military jet fuels include JP-4, JP-5 and JP-8. For example, Jet A, Jet A-1, JP-5 and JP-8 are kerosene-type jet fuels that include hydrocarbons numbering between about 8 and 16 carbon atoms. Jet B and JP-4, on the other hand, is typically a naphtha-type jet fuel having hydrocarbons numbering between about 5 and 15 carbon atoms.

In certain embodiments, the additive composition of the present invention for the reduction of particulate matter production during the combustion of jet fuel in jet engines includes an aliphatic compound or mixture of aliphatic compounds having a boiling point that is between about 200° C. and about 325° C., more preferably between about 230° C. and about 315° C. In certain embodiments, the aliphatic compound or mixture of aliphatic compounds can have a boiling point of between about 180° C. and about 300° C. In other embodiments, the additive composition can have a boiling point of between about 200° C. and about 250° C. In other embodiments, the additive can have a boiling point of between about 240° C. and about 315° C. In yet other embodiments, the additive can have a boiling point of between 250° C. and about 275° C. In certain embodiments, the additive composition can have a boiling point of between about 210° C. and about 235° C. In certain embodiments, the additive composition can have a boiling point of between about 220° C. and about 255° C. In certain embodiments, the additive composition can have a boiling point of between about 220° C. and about 240° C. In certain embodiments, the additive composition can have a boiling point of between about 270° C. and about 310° C. In certain embodiments, the additive composition can have a boiling point of between about 250° C. and about 290° C. In certain embodiments, the additive composition can have a boiling point of between about 260° C. and about 300° C.

In certain embodiments where the additive composition is a mixture of aliphatic compounds, it is preferred that the boiling point of each aliphatic compound contained therein is within the range specified for each embodiment. For example, if the aliphatic composition has a boiling point ranging between about 215° C. and about 310° C., it is preferred that each compound present is an aliphatic compound having a boiling point between about 215° C. and about 310° C. The mixture can consist of linear aliphatic hydrocarbons of varying lengths. Alternatively, the mixture can consist of branched aliphatic hydrocarbons of varying lengths. Alternatively, the mixture can consist of cyclic aliphatic hydrocarbons of varying lengths. In certain embodiments, the mixture may comprise one or more linear, branched and/or cyclic aliphatic hydrocarbon having a boiling point between about 200° C. and about 320°, alternatively between about 220° C. and 260° C., or alternatively between about 250° C. and 310° C.

In certain embodiments, the hydrocarbon additive is dodecane (C₁₂H₂₆). In certain embodiments, the hydrocarbon additive is tridecane (C₁₃H₂₈). In certain embodiments, the hydrocarbon additive is tetradecane (C₁₄H₃₀). In certain embodiments, the hydrocarbon additive is mainly pentadecane (C₁₅H₃₂). In certain embodiments, the hydrocarbon additive is hexadecane (C₁₆H₃₄). In certain embodiments, the hydrocarbon additive is heptadecane (C₁₇H₃₆).

The additive composition may include branched or alkyl substituted hydrocarbons, such as methyl and ethyl substituted hydrodrocarbons. For example, in certain embodiments, the additive composition can include a hydrocarbon selected from undecane, dodecane, tridecane, tetradecane, and pentadecane, wherein the hydrocarbon includes at least one methyl or ethyl substituent. Exemplary substituted aliphatic hydrocarbons include 2-methyl dodecane and complex mixtures of linear and branched aliphatic compounds and mixture of linear, branched and cyclic compounds.

The additive composition may include aliphatic cyclic hydrocarbons, such as cyclodecane (C₁₀H₂₀), cyclododecane (C₁₂H₂₄), and the like.

In certain embodiments, the additive can include a range of different aliphatic hydrocarbons, wherein the aliphatic hydrocarbons each have a boiling point of between about 200° C. and about 320′, preferably between about 215° C. and about 310°. For example, in one embodiment the additive can include a mixture of hydrocarbons ranging from about C₁₂ to C₁₅, wherein the major constituent is C₁₃. In an alternate embodiment the additive can include a mixture of hydrocarbons ranging from about C₁₃ to C₁₈, wherein the major constituent is C₁₅.

In certain embodiments, the fuel composition of the present invention can include up to about 50% by weight of the additive composition, preferably up to about 35%. Thus, in one exemplary embodiment, a fuel composition that includes between about 85% and 90% by weight jet fuel and between about 10% and 15% by weight of the additive composition is provided. In another embodiment, a fuel composition that includes between about 75% and 85% by weight jet fuel and between about 15% and 25% by weight of the additive composition is provided.

In certain embodiments of the present invention, between about 5% and 10% by weight of the aliphatic additive is added to the jet fuel. In yet other embodiments, between about 10% and 15% by weight of the aliphatic additive is added to the jet fuel. In alternate embodiments, between about 15% and 20% by weight of the aliphatic additive is added to the jet fuel. Other embodiments include between about 20% and 25% by weight of the aliphatic additive in the jet fuel. In yet other embodiments, the jet fuel includes at least about 25% by weight of the aliphatic additive.

In certain embodiments, the jet fuel can first be treated to remove a portion of the aromatic compounds present. In certain embodiments, between about 1 and 5% of the aromatic compounds can be removed before the aliphatic additive is added to the jet fuel.

In certain embodiments, the additive composition can also include additives, such as, antioxidants, corrosion inhibitors, icing inhibitors, biocides, lubricants, and/or antistatic agents.

In certain embodiments, the addition of a soot reduction additive as described herein can be coupled with a method for the removal of at least a portion of the aromatic hydrocarbons present in the jet fuel.

Particulate matter in jet fuel exhaust can be measured by known means, such as with an engine exhaust particle sizer (EEPS), Scanning Mobility Particle Sizer (SMPS, capable of measuring particles having a diameter from about 2.5 nm to 1000 nm), or a Smoke Meter. The EEPS (Model 3090 Engine Exhaust Particle Sizer) is designed specifically for measuring particles emitted from internal combustion engines in “realtime”, and is capable of measuring particles having a diameter from about 5.6 nm to 560 nm, with a sizing resolution of 16 channels per decade (a total of 32 channels). The EEPS can measure particle size, distribution, and total concentration of particulate in “real time”. Particles of the aerosol enter the spectrometer through a cyclone which removes large particles and the remaining particles pass through an electrical diffusion charge in which ions are generated. The ions mix with the particles and electrically charge them to a predictable charge level based on the particle size. The charged particles enter a sizing region formed by the space between two concentric cylinders. The outer cylinder includes electrodes connected to a charge amplifier (electrometer) with an input near ground potential wherein the inner cylinder is connected to a positive high voltage supply creating an electric field between the two cylinders. The positively charged particles flow from top to bottom of the sizing region, are repelled from the high voltage electrode, and travel towards the sensing electrodes. Particles that land on the sensing electrodes transfer their charge, thereby producing a current that is amplified by the electrometers, digitized, and read by a microcontroller. This data is processed in real time to obtain 10 particle size distributions per second. The entire system can be automated and data analysis can be done with EEPS software.

EXAMPLES

Combustion experiments for the jet fuel-additive compositions described herein were conducted with a vertically oriented combustor burner operated at atmospheric pressures wherein the fuel-additive composition flowed upwardly. The burner includes a 4 in. stainless steel air duct, a 2 in. co-axial center body, an air-atomized liquid fuel nozzle, a hot-surface or spark igniter and a 4 in. diameter stainless steel exhaust chimney. Above the stainless steel chimney, a perforated 0.25 in. tube traversed the exhaust duct approximately 2 in. below dump plane. Combustion and atomization air were supplied to the test stand using house air at about 90 psig. Two syringe pumps supplied liquid fuel containing the baseline fuel Jet-A and the experimental additive.

The syringe pumps were operated simultaneously to delivery a constant volume of fuel to the combustor for the duration of the experiment. Delivery of the natural gas was used to pilot the combustion of the liquid fuel to stabilize and hold a flame in the combustor. The fuel-additive composition was dispersed with atomizing air into the combustion chamber with a 30610-8 Delevan nozzle. The liquid fuel and atomizing air were delivered through the air atomizing nozzle. The natural gas pilot was delivered through the center body. The natural gas was delivered through small injection ports in a concentric circle between the centerline of the center body and the outer diameter of the center body. Feed rates were 2 mL/min liquid fuel-additive composition feed, 2 slpm natural gas feed to pilot the combustion process, 5 slpm atomizing air, and 25.4 slpm combustion air, resulting in an approximate Phi=1.17.

Each experiment was conducted for 50 min., wherein a baseline reference sample was run for about 20 min., followed by a gradient of 100% baseline fuel at the beginning of the experiment to 100% of the fuel-additive composition at the end of the gradient over a period 30 min.

Particulate matter was measured as the number of particulates per cubic centimeter with an EEPS, as previously described herein.

Referring now to FIG. 1, the effect of increasing the concentration of an aliphatic hydrocarbon in a fuel composition that includes Jet A is shown. As shown in FIG. 1, production of particulate matter from a jet engine combusting a Jet A fuel composition that includes up to about 50% by weight dodecane is provided. As shown in the Figure and as provided in Table 1 below, at a dodecane additive concentration of about 10% by weight, particulate matter production is reduced by about 14%, as compared to the fuel composition without the additive. Similarly, at a dodecane additive concentration of about 30% by weight, particulate matter production is reduced by about 71%, as compared to the fuel composition without the dodecane additive.

Referring now to FIG. 2, another example demonstrating the effect of increasing the concentration of the aliphatic hydrocarbon in a fuel composition that includes Jet A is shown. As shown in FIG. 2, production of particulate matter from a jet engine combusting a Jet A fuel composition that includes up to about 35% by weight cyclododecane is provided. As shown in the Figure and as provided in Table 1 below, at a cyclododecane additive concentration of about 10% by weight, particulate matter production is reduced by about 19%, as compared to the fuel composition without the additive. Similarly, at a dodecane additive concentration of about 30% by weight, particulate matter production is reduced by about 83%, as compared to the fuel composition without the dodecane additive.

Referring now to FIG. 3, the effect of increasing the concentration of a mixture of aliphatic hydrocarbons in a fuel composition that includes Jet A is shown. As shown in FIG. 2, production of particulate matter from a jet engine combusting a Jet A fuel composition that includes up to about 50% by weight of a mixture of linear aliphatic hydrocarbons having a boiling point range of between about 220° C. and 245° C. is provided. As provided in Table 1 below, at an additive concentration of about 10% by weight, particulate matter production is reduced by about 21%, as compared to the fuel composition without the additive. Similarly, at an additive concentration of about 30% by weight, particulate matter production is reduced by about 86%, as compared to the fuel composition without the additive.

Referring now to FIG. 4, production of particulate matter from a jet engine combusting a Jet A fuel composition that includes up to about 50% by weight of a mixture of aliphatic hydrocarbons having a boiling point range of between about 245° C. and 275° C. is provided. As provided in Table 1 below, at an additive concentration of about 10% by weight, particulate matter production is reduced by about 28%, as compared to the fuel composition without the additive. Similarly, at an additive concentration of about 30% by weight, particulate matter production is reduced by about 89%, as compared to the fuel composition without the additive.

Referring now to FIG. 5, production of particulate matter from a jet engine combusting a Jet A fuel composition that includes up to about 50% by weight of a mixture of branched aliphatic hydrocarbons having a boiling point range of between about 220° C. and 255° C. is provided. As provided in Table 1 below, at an additive concentration of about 10% by weight, particulate matter production is reduced by about 6%, as compared to the fuel composition without the additive. Similarly, at an additive concentration of about 30% by weight, particulate matter production is reduced by about 61%, as compared to the fuel composition without the additive.

Referring now to FIG. 6, production of particulate matter from a jet engine combusting a Jet A fuel composition that includes up to about 50% by weight of a mixture of branched aliphatic hydrocarbons having a boiling point range of between about 270° C. and 310° C. is provided. As provided in Table 1 below, at an additive concentration of about 10% by weight, particulate matter production is reduced by about 17%, as compared to the fuel composition without the additive. Similarly, at an additive concentration of about 30% by weight, particulate matter production is reduced by about 69%, as compared to the fuel composition without the additive.

Referring now to FIG. 7, for comparison purposes, the effect of adding between up to about 50% by weight an aliphatic hydrocarbon additive having a boiling point less than 200° C. to a Jet A fuel composition that includes is shown. Specifically, FIG. 7 illustrates the effects of adding up to about 50% by weight of decane, an aliphatic hydrocarbon having a boiling point of about 174° C. As shown in FIG. 7 and provided in Table 1 below, at an decane concentration of about 10% by weight, particulate matter production increases by about 13%, as compared to the Jet A fuel composition without the added decane. Similarly, at a decane concentration of about 30% by weight, particulate matter production is increased by about 26%, as compared to the fuel composition without the added decane.

TABLE 1 % PARTICULATE REDUCTION Example 2 % Additive Example 1 Cyclo- Example 7 in Jet A (Dodecane) dodecane Example 3 Example 4 Example 5 Example 6 (Decane) 10% 14 19 21 28 6 17 113 20% 38 55 71 74 46 48 113 30% 71 83 86 89 61 69 126 40% 83 — 92 93 75 81 143 50% 89 — 94 95 77 84 156

In another aspect, the present invention provides a method for reducing particulate matter in an exhaust stream from a jet engine. The method includes the step of combusting a jet fuel in a jet engine, wherein the jet fuel includes a particulate reduction or soot reduction additive. The additive is preferably an additive as previously described, i.e., an aliphatic hydrocarbon additive having a straight chain, branched or cyclic geometry, at least 10 carbon atoms, and a boiling point between about 200° C. and about 300°. In certain embodiments, the additive may be present in an amount up to about 30% by weight. In other embodiments, the jet fuel to particulate reduction additive is up to about 7:3. In alternate embodiments, the ratio of jet fuel to particulate reduction additive is between about 7:3 and 9:1.

One major advantage to the present invention is the ease of use of the method for reducing the production of particulate matter. In certain embodiments, an additive composition according to the present invention is added directly to the jet fuel to provide

Although the present invention has been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereupon without departing from the principle and scope of the invention. Accordingly, the scope of the present invention should be determined by the following claims and their appropriate legal equivalents.

The singular forms “a”, “art” and “the” include plural referents, unless the context clearly dictates otherwise.

Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

Throughout this application, where patents or publications are referenced, the disclosures of these references in their entireties are intended to be incorporated by reference into this application, in order to more fully describe the state of the art to which the invention pertains, except when these reference contradict the statements made herein. 

1. A jet fuel composition for producing an exhaust having reduced particulate matter, comprising: a jet fuel; and an additive comprising an aliphatic hydrocarbon compound having at least 10 carbon atoms; wherein the aliphatic hydrocarbon additive has a boiling point of between about 215 and 310° C.
 2. The jet fuel composition of claim 1 wherein the jet fuel is present in an amount of at least 65% by weight and the additive is present in an amount between about 5 and 35% by weight.
 3. The jet fuel composition of claim 1 wherein the jet fuel is present in an amount of between about 80 and 90% by weight and the additive is present in an amount of between about 10 and 20% by weight.
 4. The jet fuel composition of claim 1 wherein the jet fuel is present in an amount of between about 20 and 35% by weight and the additive is present in an amount of between about 65 and 80% by weight.
 5. The jet fuel composition of claim 1 wherein the additive is selected from dodecane, cyclododecane, tridecane, tetradecane and pentadecane.
 6. The jet fuel composition of claim 1 wherein the additive comprises an aliphatic hydrocarbon having between about 12 and 15 carbon atoms.
 7. The jet fuel composition of claim 1 wherein the jet fuel is selected from the group consisting of Jet A, Jet A-1, Jet B, JP-4, JP-5, and JP-8.
 8. The jet fuel composition of claim 1 wherein the aliphatic additive is a straight chain hydrocarbon
 9. The jet fuel composition of claim 1 wherein the aliphatic additive is a cyclic hydrocarbon.
 10. The jet fuel composition of claim 1 wherein the aliphatic additive is a mixture of branched and straight chain hydrocarbons.
 11. A method for reducing particulate matter in an exhaust from a jet engine, comprising: combusting a jet fuel in a jet engine; wherein said jet fuel comprises an additive for reducing the amount of particulate matter present in said exhaust, said additive comprising an aliphatic hydrocarbon having at least 10 carbon additives and a boiling point of between about 230 and 310° C.
 12. The method of claim 11 wherein the soot reduction additive is present in an amount of up to about 35% by weight.
 13. The method of claim 11 wherein the soot reduction additive is present in an amount of between about 10 and 25% by weight.
 14. The method of claim 11 wherein the soot reduction additive is present in an amount of between about 15 and 30% by weight.
 15. The method of claim 11 wherein the soot reduction additive is selected from the group consisting of dodecane, cyclododecane, tridecane, tetradecane and pentadecane. 